How can I determine the proper stressing of words?

I highly recommend Stephen Fry's "The Ode Less Travelled". He starts by explaining the various rhythms of iambic pentameter, including all the various substitutions and how to use them effectively, and provides exercises to help you.

I wrote a poem about software development in Iambic Pentameter recently after reading this book. Iambic pentameter normally follows this rhythm:

da-DA da-DA da-DA da-DA da-DA

Or, using the notation you suggested:

da da' da da' da da' da da' da da'

An iamb is a foot, and there are five of them, hence pentameter. You can occasionally substitute the iambs, and it's also OK to put a falling note after the last iamb since most words in English end that way. Hopefully my poem provides you with some examples of this, but I would still recommend the book.